Notallsoundsmadebyanimalsserveaslanguage,andwehaveonlytoturntothatextraordinarydiscoveryofecholocation(回声定位)inbatstoseeacaseinwhichthevoiceplaysastrictlypracticalrole.
Togetafullappreciationofwhatthismeanswemustturnfirsttosomerecenthumaninventions.Everyoneknowsthatifheshoutsnearawalloramountainside,anechowillcomeback.Thefurtheroffthissolidobstacle,thelongertimeitwilltakeforthereturnoftheecho.Asoundmadebytappingonthemainbodyofashipwillbereflectedfromtheseabottom,andbymeasuringthetimeintervalbetweenthetapsandthereceiptoftheechoesthedepthoftheseaatthatpointcanbecalculated.Sowasborntheecho-soundingequipment,nowingeneraluseinships.Everysolidobjectwillreflectasound,varyingaccordingtothesizeandnatureoftheobject.Ashoaloffishwilldothis.Soitisacomparativelysimplestepfromlocatingtheseabottomtolocatingashoaloffish.Withexperience,andwithimprovedequipment,itisnowpossiblenotonlytolocatefishbuttotellifitisherring,cod,orotherwell-knownfish,bythepatternofitsecho.
Afewyearsagoitwasfoundthatcertainbatsemitsqueaks(吱吱声)andbyreceiving’heechoestheycouldlocateandsteerclearofobstacles--orlocateflyinginsectsonwhichtheyfeed.Thisecholocationinbatsisoftencomparedwithradar,theprincipleofwhichissimilar.
练习题：
Choosecorrectanswerstothequestion:
1.Themainpurposeofthispassageisto______.
A.describethatanimalscanmakedifferentsounds
B.provethatanimals’voicescanplaypracticalroles
C.inspirethereaderstomakemoreinventions
D.startlethereaderswithsomeshockingfacts
2.ThediscoveryofecholocationmayhelpwithallofthefollowingEXCEPT
A.measuringthedepthofthesea
B.distinguishingdifferentkindsoffish
C.improvingthefunctionsofradar
D.varyingthesizeandnatureofanobject
3.Bysaying"Ashoaloffishwilldothis"(Lines6-7,Para.2),theauthormeans________.
A.onlyonespecialkindoffishcanreflectsounds
B.onlyonespecialkindoffishcanbeusedtohelplocateaship
C.alargegroupoffishcanreflectsounds
D.alargegroupoffishcanbeusedtohelplocateaship
4.Asitisdiscussedinthepassage,thesqueaksofbatscanbefunctionallycomparedwith________.
5.Whichofthefollowingstatementscanbeinferredfromthepassage?
A.Animalsaremoreintelligentthanhumans.
B.Humansaremoreintelligentthananimals.
C.Animalsareoftencomparedwithhumaninventions.
D.Humansareofteninspiredbyanimals.
